The present invention relates to a distribution device notably intended for an automatic equipment allowing multi-reactor testing of chemical reactions, possibly in the presence of a catalyst. For this type of equipment to work under high pressure and high temperature conditions, it necessarily comprises a distribution device withstanding these conditions while operating a system intended for in-line analysis of the reaction products. The present invention can be advantageously automated so that the multi-reactors can be used in parallel. Fast and simultaneous evaluation of several sets of operating conditions thus allows acquisition of data on the progress of the reaction and on the performances of solid catalysts.
In-line analysis is possible through precise control of the temperature and of the total and partial pressures of the products coming from the reactors. The distribution device must also allow such control. The elaborate automation of the assembly allows to carry out simultaneous cycles of all the reactors without the operator""s intervention.
The development of industrial refining and petrochemical processes requires acquisition of data on the chemical reactions that take place. When these reactions are catalyzed, research and development of the catalysts required involve evaluation of the performances thereof. In the laboratory, these data acquisitions and evaluations are performed in pilot plants which reproduce on a small scale the industrial operating conditions.
There are many types of equipments allowing to measure the rate of progress of chemical reactions or the activity of solid catalysts. In the field of petroleum refining and of petrochemistry, the operating conditions under which these measurements are performed are as follows:
pressure ranging between 1.105 and 3.107 Pa,
temperature ranging between ambient temperature and 800xc2x0 C.,
liquid and/or gaseous reagent flow rates expressed in form of hourly volume flow rate per unit of volume of reactor or catalyst (hourly space velocity) ranging between 0.01 and 100 hxe2x88x921 and by the ratio of the molar flow rate of gas (most often hydrogen) and the liquid reactive hydrocarbon (H2/HC) ranging between 0.01 and 50.
More precise selection of the operating conditions depends on the type of process or of catalyst considered. It can be, for example, one of the following industrial applications: reforming, isomerization, hydrocracking, hydrotreating, selective hydrogenation, conversion of aromatics or oxidation.
Solid catalysts are used as balls, extrudates or powder of variable grain size. The quantities of catalysts used in these pilot plants generally range between some grams and several ten or hundred grams. These quantities are relatively great and they can be a limitation to the use of these pilot plants. In particular, during research or development of a new catalyst, the quantities of solid catalyst available for testing are quite often limited (less than one gram) and there can be a great number of catalytic solid variants. All the available samples are therefore not necessarily tested.
The most isothermal operating conditions possible are sought for the reactors. This is generally obtained by placing the reactor in an oven consisting of several zones whose temperature is independently controlled (U.S. Pat. No. 5,770,154). The dimensions of the reactors also receive particular attention. In particular, the length/diameter ratio of the catalyst bed is most often selected between 50 and 200 so as to ensure proper flow of the reagents and of the products through the catalyst, failing which diffusion or backmixing limiting phenomena disturb measurement of the progress rates and performances of the catalyst.
Catalysts generally require, prior to the reaction stage proper, an activation stage which changes one or more of their constituents into a really active element for catalysis. It may be an oxide reduction in hydrogen in the case of supported metal catalysts or sulfurization in the presence of a sulfur-containing forerunner for catalysts based on metal sulfides. In conventional pilot plants with large dead volumes and a great thermal inertia because of the size of the ovens, this activation stage is generally long (typically of the order of several hours to several ten hours).
The nature of the reagent used (most often a hydrocarbon or a mixture of hydrocarbons) depends on the application considered. It can be a pure hydrocarbon such as, for example, normal hexane, normal heptane or cyclohexane, or more or less heavy or more or less wide petroleum cuts such as, for example, gasolines, gas oils or distillates from crude oil distillation. The quantities of reagent consumed depend of course on the size of the reactor and on the operational time. Most often, however, the performances are calculated from inlet-outlet material balances performed over relatively long periods (some hours to several ten hours). These periods are necessary to allow to collect a sufficient amount (several liters to several ten liters) of products in order to draw up a precise material balance. Using a pure hydrocarbon-containing molecule whose manufacturing cost is high is not always possible under such conditions.
Furthermore, during the period of evaluation of the material balance, which can be long, the catalyst may undergo a certain deactivation. Since the activity of the catalyst is not the same between the beginning and the end of the material balance, the performances calculated in fine only reflect an average behaviour of the catalyst, far from the real evolution of the performances in time.
The effluents coming from the reactor are conventionally separated by expansion and cooling into two phases: liquid and gaseous, whose characteristics and compositions are analyzed separately. These separate separation and analysis operations inevitably lead to product losses which reduce the accuracy of the global material balance. In some cases, analysis of all of the products cannot be carried out at one go with a single chromatographic analyzer. It is then possible to perform an in-line analysis before liquid/gas separation together with an analysis of the gaseous fraction taken after separation. This allows to draw up accurate material balances in this case (U.S. Pat. No. 5,266,270).
Automation of conventional pilot plants remains quite often underdeveloped. The size of these plants and observance of the safety regulations linked with automatic operation make this automation complex and expensive. In particular, the operating conditions determining the severity with which the reaction progresses (temperature or volume flow rate of the reagent) are most often manually adjusted by the plant operator.
To sum up, the conventional pilot plants commonly used for measuring the progress of chemical reactions and the performances of catalysts have a certain number of drawbacks, such as:
the necessity for a large quantity of catalyst and of reagent,
the length of the set-up time and the time required for drawing up the material balance required to determine the performances,
the performances reflect an average behaviour of the catalyst over a relatively long period,
the performance measurement frequency is relatively low,
complete operation automation is difficult and expensive.
On account of these drawbacks, conventional pilot plants are not very well suited for fast and precise screening, among many catalytic solids, of the most interesting solids for development of a new catalyst or study of a new reaction.
The present invention thus relates to a distribution device notably intended for a gaseous effluent produced by a chemical reaction, comprising at least two inlet ways and two outlet ways. The device comprises at least one closed-loop line divided into four sections by four controlled sealing elements, each one of said ways communicates with a single section so that the inlet ways are connected to two opposite sections and said outlet ways are connected to the other two sections.
The device can comprise two closed-loop lines and the outlet ways communicate together two by two so as to form a distribution device with four inlet ways and two outlet ways.
The sealing elements can consist of a conical needle cooperating with a sealed seat.
The sealing elements can be controlled by a pneumatic jack type operator.
The closed-loop line can consist of four rectilinear lines arranged in the shape of a quadrilateral, the sealing elements being substantially located at the four corners of the quadrilateral.
The sealing elements can be suited for an effluent pressure and temperature that can reach 250 b and 400xc2x0 C. respectively.
The distribution device according to the invention can be applied to an equipment for performing measurements on an effluent resulting from a chemical reaction taking place in a reactor containing a catalyst, and comprising:
at least two reactors,
effluent analysis and measuring means,
means intended for automatic monitoring and control of the chemical reaction and of the analysis and measurement cycle,
the device supplying the analysis and measuring means alternately with the effluents from the two reactors in order to perform analysis and measurement cycles on two reactions progressing in parallel.
The following advantages of the device according to the invention can notably be mentioned:
automatic measurement of the progress of chemical reactions and of catalytic performances in parallel in several reactors,
possible control of the partial pressures and temperatures of the effluents in order to allow single and complete analysis without separation into several fractions,
selective and frequent measurement of the reaction and catalytic performances,
higher performance determination accuracy thanks to the limited dead volumes,
complete progress of the operating cycles without the operator""s intervention.